In recent years increased interest and efforts have been exerted in order to avoid waste of energy both for cooling and heating of homes and buildings. It has been noted that a case of energy waste obtains when a heated or cooled room is thrown open to the environment, e.g. by opening windows or doors without turning off the source of heating and cooling.
This applies to both residential and even more to public buildings where considerable amounts of energy can be wasted by carelessly throwing open large windows and doors in large rooms without turning off the heating or cooling supply for that room.
A body of prior art addressing this problem has been uncovered by applicant. In particular, U.S. Pat. No. 3,729,735 relates to a remote ultrasonic sending device for air conditioners, which discloses a remote sending device controlled by opening or closing of a window by means of a window actuator connected to an ultrasonic transmitter using one or more tuning forks to control a motor switch to activate or deactivate a blower motor of an air-conditioning system for a given area. This arrangement has the drawbacks that very large or noisy rooms may create interference with a system which is based on acoustic signaling, and that acoustic signals may be obstructed by curtains, walls, etc.
U.S. Pat. No. 4,223,831 provides a system wherein the environmental temperature in an area is controlled by the detection of the presence or absence of personnel in a room. A microphone detects sounds in the room and actuates a control circuit to establish a set point for a temperature system which supplies heating and cooling to the room. The presence of people in the room is accompanied by sounds which are detected by the microphone to set the set point at an appropriate temperature to provide a comfortable environment. The absence of sound permits a new set point to be used to reduce the energy consumption of the heating or cooling system. A time delay circuit is optionally incorporated to eliminate undesirable cycling.
U.S. Pat. No. 4,493,100 shows a system wherein voice commands of two types are recognized by an air conditioner; a first command to jump to a different air delivery temperature, after which a gradual automatic return to the previously set temperature occurs, or a second command which will stop the automatic return at some arbitrary temperature.
U.S. Pat. No. 4,035,796 shows a system which includes a simple apparatus for turning off a heating or air conditioning unit when a door or window is opened. Switches activated by the opening of doors or windows control the operation of a heater or air conditioner through a relay system that doubles as a burglar alarm when an alarm circuit is activated.
None of the prior art known to applicant provides features shown by applicant, namely a system which is readily suitable for large as well as small buildings, and has a high degree of safety against an unwanted operation caused by acoustic or other kinds of interference.